Interpretive Summary: Much attention has been given to developing a national animal identification program to allow traceability of animals throughout the production process. Use of radio frequency identification (RFID) ear tags is one method currently being considered for lifetime identification. For this technology to fulfill the requirements of a national animal identification program, knowledge of the retention and function of the tags is needed. To provide insight into functionality of RFID tags over a long term, 1 of 5 types of RFID tags was applied in the ear of a total of 4316 cows on 4 separate ranches. Tags were evaluated at approximately yearly intervals for either 2 (Ranch 1), 3 (Ranches 2 and 3) or 5 yrs. Percent of tags that were lost or that failed to read were 1.4, 1.6, 3.7, 5.1, and 5.0 for the 5 consecutive annual evaluations, respectively when summarized across ranches and RFID tag type. Cumulative losses of 3.0, 6.0, and 19.8 % were observed when summarized over all tag types after 2 (all 4 ranches), 3 (3 ranches) and 5 years (1 ranch). These results provide evidence that losses and failure of RFID tags over long periods of time may diminish the fidelity of this methodology for identifying individual animals as part of a national animal identification program. These results also indicate the need for considering impact of retagging on structure of any database, where the EID would presumably be used as the primary identifier.

Technical Abstract:
Objective of this study was to evaluate failure (loss or inability to read) of radio frequency identification (RFID) ear tags in beef cows over a 2 to 5 year period under ranching conditions. One of 5 types of RFID tags was applied in the ear of a total of 4316 cows on 4 separate ranches. Tags were evaluated at approximately yearly intervals for either 2 (Ranch 1), 3 (Ranches 2 and 3) or 5 yrs. Percent of tags that were lost or that failed to read were 1.4, 1.6, 3.7, 5.1, and 5.0 for the 5 consecutive annual evaluations, respectively when summarized across ranches and RFID tag type. Cumulative losses of 3.0, 6.0, and 19.8 % were observed when summarized over all tag types after 2 (all 4 ranches), 3 (3 ranches) and 5 years (1 ranch). A ranch by tag type interaction was evident for failure of the 2 types of tags evaluated on all 4 ranches; a greater proportion of Allflex HDX tags were lost than Allflex FDX tags at Ranch 4 (36 vs. 4%), but not other ranches (4.7 vs. 5.1% cumulative loss/fail rate for HDX and FDX). This interaction may be due to differences in tag placement. Tags were placed in the top of the ear at Ranch 4, but were attached between 2nd and 3rd ribs of the ear at Ranches 1, 2 and 3. Results indicate that loss of RFID tags increases with time after application, and may exceed 5% after 3 years.